'Add component' button disappears even when screen is on Details layout

The + sign that let’s me add components is disappearing in seemingly random fashion.
Example: I opened a new tab, clicked to make it ‘details’ layout. Added a component. Deleted it again. Now I cannot add any component. Even though I recreate the tab. Even if I use data that works on other screens. I’m probably doing something wrong, but cannot figure out what it is, help is very much appreciated!

If you refresh the builder, does that fix it?
If not, I’d suggest signing out of Glide, delete anything Glide related from your browser cookie store and cache, and then try again.

Do you have columns in the table that is the data source of the screen?